An international standardization project, 3GPP (3rd Generation Partnership Project) is discussing specifications of a network developed from W-CDMA (Wideband-Code Division Multiple Access) and GSM (Global System for Mobile Communications) as a system of next-generation cellular mobile communication.
3GPP has been discussing cellular mobile communication systems for a long time and has standardized the W-CDMA system as a third-generation cellular mobile communication system. HSDPA (High-Speed Downlink Packet Access) with higher communication speed has been standardized and the service is operated. 3GPP is currently also discussing development of the third-generation radio access technology (Long Term Evolution, hereinafter referred to as “LTE”) and LTE Advanced (hereinafter referred to as “LTE-A”) aimed at further increase in communication speed.
The OFDMA (Orthogonal Frequency Division Multiple Access) method and the SC-FDMA (Single Carrier-Frequency Division Multiple Access) method which perform user-multiplexing using subcarriers that are at right angles to each other are discussed as communication systems in LTE. Specifically, the OFDMA method is a multi-carrier communication method and is proposed for downlink, and the SC-FDMA method is a single-carrier communication method and is proposed for uplink.
On the other hand, for communication methods in LTE-A, it is discussed to introduce the OFDMA method for downlink and the Clustered-SC-FDMA (Clustered-Single Carrier-Frequency Division Multiple Access, also referred to as DFT-s-OFDM with Spectrum Division Control or DFT-precoded OFDM) method for uplink in addition to the SC-FDMA method. The SC-FDMA method and the Clustered-SC-FDMA system proposed as uplink communication methods in LTE and LTE-A are characterized in that PAPR (Peak to Average Power Ratio) at the time of transmission of data (information) can be suppressed to a lower level.
While a typical mobile communication system uses a continuous frequency band, it is discussed for LTE-A to use a plurality of continuous/non-continuous frequency bands (hereinafter referred to as “carrier elements, carrier components (CC)” or “element carriers, component carriers (CC)”) in a composite manner to implement operation as one frequency band (a wider frequency band) (frequency band aggregation, also referred to as spectrum aggregation, carrier aggregation, and frequency aggregation). It is also proposed to give different frequency bandwidths to a frequency band used for downlink communication and a frequency band used for uplink communication so that a base station apparatus and a mobile station apparatus more flexibly use a wider frequency band to perform communication (asymmetric frequency band aggregation: asymmetric carrier aggregation) (Non-patent Literature 1).
FIG. 8 is a diagram for explaining frequency band aggregation in a conventional technique. Giving the same bandwidth to a frequency band used for downlink (DL) communication and a frequency band used for uplink (UL) communication as depicted in FIG. 8 is also referred to as symmetric frequency band aggregation (symmetric carrier aggregation). As depicted in FIG. 8, a base station apparatus and a mobile station apparatus use a plurality of component carriers that are continuous/non-continuous frequency bands in a composite manner, thereby performing communication in a wider frequency band made up of a plurality of component carriers. In this case, byway of example, it is depicted that a frequency band used for the downlink communication with a bandwidth of 100 MHz (hereinafter also referred to as a DL system band or a DL system bandwidth) is made up of five component carriers (DCC1: Downlink Component Carrier 1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz. By way of example, it is also depicted that a frequency band used for the uplink communication with a bandwidth of 100 MHz (hereinafter also referred to as a UL system band or a UL system bandwidth) is made up of five component carriers (UCC1: Uplink Component Carrier 1, UCC2, UCC3, UCC4, and UCC5) each having a bandwidth of 20 MHz.
In FIG. 8, downlink channels such as a physical downlink control channel (hereinafter, PDCCH) and a physical downlink shared channel (hereinafter, PDSCH) are mapped on each of the downlink component carriers. And the base station apparatus uses the PDCCH to transmit to the mobile station apparatus control information for transmitting a downlink transport block transmitted by using the PDSCH on each of the downlink component carriers (such as resource allocation information, MCS (Modulation and Coding Method) information, and HARQ (Hybrid Automatic Repeat ReQuest) process information) (uses the PDCCH to allocate the PDSCH to the mobile station apparatus) and uses the PDSCH to transmit the downlink transport block to the mobile station apparatus.
Uplink channels such as a physical uplink control channel (hereinafter, PUCCH) and a physical uplink shared channel (hereinafter, PUSCH) are mapped on each of the uplink component carriers. And the mobile station apparatus uses the PUCCH and/or the PUSCH on each of the uplink component carriers to transmit to the base station apparatus control information of HARQ (hereafter described as HARQ control information) for the PDCCH and/or the downlink transport block. The HARQ control information includes a signal (information) indicative of ACK/NACK (Positive Acknowledgement/Negative Acknowledgement, ACK signal or NACK signal) and/or a signal (information) indicative of DTX (Discontinuous Transmission) for the PDCCH and/or the downlink transport block. The DTX is a signal (information) indicating that the mobile station apparatus cannot detect the PDCCH from the base station apparatus (or may be a signal (information) indicative of whether the mobile station apparatus can detect PDCCH). In FIG. 8, any of downlink/uplink channels such as the PDCCH, the PDSCH, the PUCCH, and the PUSCH may not be mapped on some downlink/uplink component carriers.
Similarly, FIG. 9 is a diagram for explaining asymmetric frequency band aggregation in a conventional technique. As depicted in FIG. 9, the base station apparatus and the mobile station apparatus give different bandwidths to a frequency band used for downlink communication and a frequency band used for uplink communication and use component carriers making up these frequency bands in a composite manner, thereby performing communication in a wider frequency band. In this case, by way of example, it is depicted that a frequency band used for the downlink communication with a bandwidth of 100 MHz is made up of five downlink component carriers (DCC1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz, and that a frequency band used for the uplink communication with a bandwidth of 40 MHz is made up of two component carriers (UCC1 and UCC2) each having a bandwidth of 20 MHz. In FIG. 9, downlink/uplink channels are mapped on each of the downlink/uplink component carriers. And the base station apparatus uses the PDSCH allocated by the PDCCH to transmit a transport block to the mobile station apparatus. And the mobile station apparatus uses the PUCCH and/or the PUSCH to transmit the HARQ control information to the base station apparatus.
To transmit the HARQ control information for transmission of PDCCHs and/or PDSCHs on a plurality of downlink component carriers, the mobile station apparatus must transmit to the base station apparatus information indicative of ACK, NACK, and DTX for a PDCCH and/or a PDSCH transmitted on each of the component carriers. For example, if the base station apparatus performs transmission of PDCCHs and/or PDSCHs on five downlink component carriers, the mobile station apparatus must supply information indicative as defined in any one of ACK, NACK, and DTX and therefore must transmit information capable of indicating the fifth power of three types of state (243 types of state) to the base station apparatus. To represent these types of state as bit information, eight bits (capable of representing 256 types of state) are required as information bits.
Non-patent Literature 2 proposes a transmission method in which abase station apparatus allocates to a mobile station apparatus a plurality of PUCCH resources for transmission of the HARQ control information such that the mobile station apparatus selects one PUCCH resource from the allocated PUCCH resources to transmit the HARQ control information to the base station apparatus by using the selected PUCCH resource. For example, the base station apparatus allocates to the mobile station apparatus the PUCCH resources corresponding to respective PDSCHs transmitted on a plurality of downlink component carriers and the mobile station apparatus selects one PUCCH resource from a plurality of PUCCH resources to transmit the HARQ control information by using the selected PUCCH resource. The base station apparatus extracts the PUCCH resource selected by the mobile station apparatus in addition to bit information transmitted by the mobile station apparatus so as to transmit/receive information indicative of the HARQ control information between the base station apparatus and the mobile station apparatus.